This invention is directed to a process and apparatus for gas purging of the interior of a bag or pouch which is being formed, filled, and sealed on a bagging type packaging machine. The atmospheric purge process and the apparatus for this process assists in formation of a better final seal on the bag and/or for introduction of specific atmospheres to be incorporated within the sealed bag or pouch.
In the packaging industry the word "seal" is used for both the hardware which forms "seals" or joints and also for the "seal" itself. Thus, side seals (hardware) form side seals (joints) between packaging films. In using the words "seal" or "seals" in this specification, if its meaning is not clear from the context of the sentence it is used in, it will be more fully identified by adjectives or synonyms.
With the advent and growth of certain industries, most particularly the fast or convenience food industry, machines have been developed which continuously form, fill and seal bags or pouches. These machines utilize continuous rolls of heat sealable film which are heat sealed together to form bags or pouches. Typically side seals or joints are continuously made between a front and a back film, a bottom seal is then made, the bag or pouch filled and the bag or pouch completed by forming a top seal.
Most of the form, fill and seal bagging machines presently utilized, are utilized for convenience foods and/or packaging of food condiments. Typically a gang of side seals, i.e. the hardware that joins the films, will be lined up in parallel across the width of the continuous front and back films. These form individual parallel side seals, i.e. elongated areas where the films are joined together, which are spaced apart from each other at varying widths of from approximately 11/2 inches, which would be utilized for condiment packaging, to approximately 12 inches, which would be utilized for food or other items. Typically the rolls of film utilized for the front and back surfaces will be approximately 12 to 24 inches in width and as such simultaneously anywhere from two to approximately a dozen or so bags or pouches can be concurrently formed, filled and sealed by the machine.
As the continuous front and back films move through the machine, at least two or more side seams (joined areas) are formed between these films. This forms the side edges of parallel bags. These side seams are then cut or severed to separate the individual parallel bags. A cross or transverse seal (joined area) is then made across the width of the film. This seal is normally made much wider than the side seals and is split such that concurrently a top seal will be made for the bottom most of two adjoining or adjacent pouches and a bottom seal will be made for the top most of the two adjoining or adjacent pouches.
After the bottom seal is made, the pouch is ready for filling with an appropriate product. The hardware utilized to fill the pouch with product and the filling process itself is dependent upon the product which is being packaged. For certain condiment packages such as catsup, mustard or the like the product is generally added to small pouches being formed in parallel with one another utilizing parallel spaced filling tubes which simply inject an aliquot of the condiment into the pouches. For other products, however, the filling operation is somewhat more complex.
Soups, sauces and other similar products are generally at least partially cooked prior to packaging. In order to prevent spoilage and to insure freshness of the product, packaging of the product while it is still hot is advantageous. Further, in certain instances it is advantageous to seal the product within the bag or pouch and concurrently exclude oxygen from the product or the pouch to inhibit certain chemical and biological processes between the product and atmospheric oxygen.
When a product is packaged while it is hot, most often steaming hot, condensation of the steam on the interior sides of the packaging can occur. This condensation will interfere with the final sealing, i.e. the formation of the top seal of the pouch or bag. Thus, it is also desirable to eliminate steam from the interior of the bag or pouch just prior to sealing of the bag or pouch.
After loading the product in the bag or pouch, the bag or pouch is sealed by forming a top seal between the two side seals. The top seal of one bag or pouch, i.e. product containing bag, is made concurrently with the bottom seal of the next adjacent empty bag or pouch. This combination cross or transverse seal is generally made utilizing a hardware component called a head seal. This forms a seal, i.e. an elongated joint between the front and back film which is wide enough to serve both as a top seal for one package and a bottom seal for another package. This head seal can include a cut off knife or an independent cut off mechanism can be located below the head seal to sever the cross seam to form individual top seals and bottom seals on adjacent bags or pouches.
Both the head seal utilized to form the bottom and top seals and the side seals (hardware) to form the side seals (joints) are generally formed of metallic elements which have resistance heaters located in these elements to heat these metallic elements. A back and a front heated metallic element are brought together squeezing the front and back films between them to seal the front and back films together to form an impervious seal or joint between these two films.
The side seals or joints can be made in a continuous manner as the rolls of the film are threaded through the side seals (hardware). The cross or transverse seal made by the head seal is formed intermittently during the cycling of the bagging machine. Thus, a cross seal is made to seal up an already filled bag and to form the bottom seam on the next bag to be loaded with product. The loaded bag is discharged from the machine simultaneously with the loading of the product in the next bag. The now newly loaded bag is then contacted once again with the head seal to form a top seal on this loaded bag and to concurrently form the bottom seal on the next bag which is to be loaded.
If water condensation takes place on the interior surfaces of the film in the area where the cross or transverse seal will be formed this can result in improper sealing of the films together resulting in the formation of voids or moisture pockets in the cross seal. If moisture was trapped in the cross seal, after severing two adjacent bags from one another the bag which has been loaded with product and sealed is susceptible to leakage. Further, the next adjacent bag being processed on the bagging machine can leak during the actual filling of the bag since it now has a perforated bottom seal.
In order to circumvent the problem of having moisture or other contaminants in the area which will ultimately form the cross seal, certain expedients have been resorted to such as squeegeeing moisture or product out of this area just prior to formation of the seal. One such apparatus for doing this is disclosed is U.S. Pat. No. 3,673,041. Such squeegeeing techniques, while being utilitarian, only attempt to correct a problem after it has occurred. They are not prophylactic in nature, that is they do not prevent the problem. If for one reason or another the squeegeeing effect is incomplete, material will be left on the films and an improper and leaking seal will result.